Keep in mind grip strength is highly correlated with testosterone : cortisol levels which is a good way to measure recovery rate. So perhaps you’re pushing too hard. Use a hand dynamometer to measure accurately like another poster has said. Reference - https://www.t-nation.com/training/4-ways-to-test-your-recovery-rate/
Also your grip strength is quite strong.
My silicone case is about 1.5 years old and the corners are starting to peel. First and last Apple case for me. I think it was $70 (cad). I feel like I should email Tim to complain.